1. Field of the Invention
The invention presented refers to a procedure for the selective influencing of natural oscillation in fine and micromechanical cantilever systems. In particular, the invention refers to magnet head suspension systems in magnetic disk drives.
2. Description of the Prior Art
Magnetic disk drives which use a transducer mounted on a slider for reading and/or writing data to at least one rotating magnetic disk are generally known. In such systems, the slider is normally coupled using a suspension system to an actuator arm. A suspension system normally consists of the base plate which creates the connection to the actuator, the actual suspension arm (load beam) and the gimbal, a flexible connecting element to the slider. The suspension is normally designed in steel.
The use of laminated materials is also known in the manufacture of slider suspension systems (see U.S. Pat. Nos. 4,996,623 and 4,761,699).
In addition, it is also known that oscillations in the arm and the suspension in magnetic disk drives can produce undesired effects such as departing from the read/write track or variations in the distance between the slider and the disk.
These oscillations occur due to the resonance phenomena at certain natural frequencies of the slider. In this, extreme mechanical influences through the drive, air flow, etc. play a part. When resonance phenomena are excited, the whole structure (suspension) is deformed in wave-type movements, so-called oscillation modes.
The aim of a so-called xe2x80x9cmodal analysisxe2x80x9d is to characterize the dynamic characteristics of the system. The modal parameters of resonance frequency, damping and form of the modes can be established experimentally or through finite-element simulation.
One known possibility for reducing such oscillations is to bring an elasto-viscous material into the suspension system supporting the slider (see U.S. Pat. No. 4,760,478, amongst others), whereby oscillation energy is converted to heat.
To damp undesired oscillations, so-called xe2x80x9cconstrained layersxe2x80x9d can also be used (see U.S. Pat. No. 5,606,477).
With the increasing storage density in information storage media such as magnetic disk drives, the necessity for slider suspension systems which reduce oscillations to a minimum is increasing.
U.S. Pat. No. 5,572,387 describes a xe2x80x9cHead Suspension Assemblyxe2x80x9d where the load beam is at least partly equipped with an elasto-viscous coating in order to dampen oscillations.
In U.S. Pat. No. 5,606,477, a slider suspension system is described which has a laminated suspension where the laminate is a conductive layer consisting of a copper alloy, a dielectric polyimide layer and a strengthening layer of special steel. A pattern of xe2x80x9cland areasxe2x80x9d is etched into the conductive layer, which function as a constraining area for the elasto-viscous dielectric layer. This construction damps existing oscillations in the suspension system.
Solutions known in the current state of technology have the disadvantage that although they damp oscillations, they are unable selectively to influence natural oscillations (characterized by resonance frequencies and the shape of modes). In this way, the oscillation modes in normal systems are already established by the form and material of the suspension. However, if one changes, for example, the external form in order to achieve an effect on oscillation modes, there is the danger that one will simultaneously inadvertently affect the air flow. Conversely, this can lead to a changed excitation of oscillations.
The invention presented is not limited to magnetic head suspension systems for magnetic disk drives. It can be used generally for fine and micromechanical systems such as cantilevers, as used in scanning probe microscopy. For the sake of simplicity, however, it is illustrated below in terms of magnetic suspension systems.
It is thus the task of the invention presented to produce a suspension which allows undesired natural oscillations in the suspension to be selectively prevented.
A further task of the invention presented is to be able to carry out a control of the oscillation modes without changing the basic material and geometric form of the suspension.
Briefly, in a preferred embodiment, the present invention comprises a suspension having a structured surface hardening. This surface hardening may be comprised of thin film stripes of material such as nitrides, carbides, and adamantine carbon. The hardened layer has a thickness in the range of 10-100 nm.
The invention has the advantage that it can be realized in fine or micromechanical systems using normal coating and photolithographic processes.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.